The invention relates to fuel-enrichment control that is operative upon starting an internal-combustion engine having electronic fuel-injection. Such an engine and control circuitry for operation of its multiple fuel injectors are illustratively shown and described in my U.S. Pat. Nos. 4,305,351, 4,349,000 and 4,523,572, to which reference is made for detailed discussion.
It suffices to say that electronic fuel-injection engines, as well as carburetor-fed engines, must confront the problem of a cold start. In the carburetor-fed engine, one resorts to a manually operable choke or to an automatic choke, which merely determines how much the air supply is to be reduced in order to transiently enrich the mixture manifolded to the cylinders. But in the fuel-injected engine, the enrichment is by lengthening the pulses which operate the injectors; in this connection, it has been a practice to provide a fixed lengthened pulse, which is operative for a preset time, illustratively 15 to 30 seconds, should an engine temperature sensor determine that a cold start is involved. In another such practice, a stretched pulse (e.g., 3 times normal duration) is applied to each fuel injector as long as there is engine cranking.
Desirable as such fuel-enrichment devices may be, the fact is that they are wasteful of fuel, and if there is a reason for difficulty in starting the engine, each restarting attempt feeds excessive fuel to the cylinders, with resultant flooding, which only adds to the problem of starting the engine.